Conventionally, dehumidifiers that combine adsorption-desorption action of the moisture adsorption member, and cooling and heating action of the heat pump have been known. For example, in Patent Literature 1, a dehumidifier having a configuration, in which a desiccant material (moisture adsorption member) in a rotor shape is disposed between a condenser and a evaporator of a heat pump so that airs of different relative humidity pass through the desiccant material, and thereby adsorption reaction and desorption reaction of moisture are repeated by rotating the desiccant material, is suggested. Moreover, the dehumidifier in Patent Literature 1 includes a heater for heating air to be dehumidified, and includes a configuration that raises evaporating temperature by supplying air heated by the heater to the evaporator, to thereby suppress frost formation on the evaporator.